Activity is a broad term that refers to any specific task, action, or process undertaken to achieve a goal or produce an outcome. Its definition varies depending on the context:

General Definition:
Activity: A condition in which things are happening or being done; a specific pursuit or task involving movement, effort, or purpose.

Contextual Definitions:
In daily life: Any action people engage in, such as walking, cooking, or reading.

In education: A structured task designed to promote learning (e.g., group discussion, lab experiment).

In business/project management: A task or set of tasks in a workflow (e.g., "Marketing activity", "Data analysis activity").

In science:

Chemistry/Physics: A measure of the effective concentration of a substance.

Biology: The functioning or behavior of a biological entity (e.g., "enzyme activity").